Conventionally, an electric wire is used as a means to supply the electric power to various devices in many places. When an electric wire is used to increase the number of devices to which the power is supplied, a power supply tap is used as an extension from a receptacle outlet installed at a wall. The electric power is supplied via the power supply tap. However, the use of the power supply tap causes many issues from the viewpoint of wiring work or accident prevention. Recently, several systems have been put into practice for efficiently supplying the electric power using an electromagnetic wave for a relatively long distance. Patent literature 1 discloses the technology that wirelessly supplies the electric power to an optical module and configures an illumination system.
The technology disclosed in patent literature 1 provides a base unit with several primary coils and provides several secondary coils and optical modules corresponding to the primary coils. The primary coil is wirelessly powered from the outside to energize the primary coil. A magnetic field resonance occurs between the energized primary coil and a secondary coil corresponding to the primary coil. The secondary coil supplies the power to an optical module to operate the optical module (to emit light). The illumination system disclosed in patent literature 1 operates the optical module but is not designed to display information such as letters or images. The illumination system does not require too many optical modules and does not require much work to place a limited number of optical modules. However, many optical modules may be needed to control on/off states of many optical modules to display information. Much work may be required to place many optical modules.
An attempt to control on/off states of many optical modules and to display information requires managing positions (i.e., addresses) of optical modules and individually controlling on/off states of respective optical modules. In this case, each optical module needs to be previously given position information (address information such as two-dimensional coordinates of two-dimensionally arranged optical modules). However, intended information cannot be displayed if optical modules are arranged based on incorrect position information. Establishment of such system requires time-consuming work such as individually confirming the position information given to each optical module to be arranged.